A Tokio Hotel fan(girl) whose favorite member of the band is Bill Kaulitz, the singer and frontman. Probably about 80% of all Tokio Hotel fans are Bill girls, with some Tom girls and those few diehard Georg or Gustav girls mixed in.

(sitting in a concert line)
Fan 1: Look at that chick. Her hair's in a huge mane and check out that leather jacket.
Fan 2: She's obviously a Bill girl.